The invention relates to an electrode for discharge lamps. An electrode of this type, used in low-pressure discharge lamps, is, for example, described on pages 137 to 139 of the book "Die Oxydkathode" (The oxide cathode), Vol. 2 by G. Hermann and S. Wagener, Johann Ambrosius Verlag, Leipzig, 2nd Edition (1950). This electrode has a rod-shaped, doubly or triply wound electrode coil made of tungsten, which is provided with an electron emitter. In standard fashion, the electron emitter consists of a mixed oxide, which contains oxides of barium, strontium and calcium. This standard emitter is usually obtained, on activation of the electrodes fitted into the lamp, from an emitter paste with 45 mol percent barium carbonate, 45 mol percent strontium carbonate and with 10 mol percent calcium carbonate, by chemical decomposition of the carbonates into the corresponding oxides. A disadvantage with this electrode is that the emitter paste must be converted from the carbonate into the oxide, since the carbon dioxide produced in this process must be removed. Furthermore, when used in cold-starting low-pressure discharge lamps, that is to say those which strike without electrode preheating, this electrode has too short a lifetime. In addition, because of its geometry and its dimensions, this electrode coil is only partially suitable for use in T1 and T2 fluorescent lamps.
Swiss Patent CH 449 117 discloses a sintered electrode for gas discharge lamps, the electron emitter of which is produced from a mixture of metal powder with oxides or peroxides of the alkaline earth metals. This mixture preferably contains two parts of oxides or peroxides of the alkaline earth metals and one part of metal powder. It is pressed into the electrode body under high pressure, about 1000-2000 kg/cm.sup.2, and then sintered. In this patent application, barium oxide is explicitly mentioned as oxide and/or peroxide, and zirconium, tantalum and tungsten are cited as metal powders. The production process for this electrode is comparatively expensive, and the electrode does not have sufficient durability in terms of cold starting. European Patent EP 0,253,316 discloses cold-startable electrodes for low-pressure discharge lamps, which essentially consists of a semiconducting porcelain. As their main component, these electrodes contain one or more oxides of the elements titanium, barium, strontium, calcium, lanthanum and tin. They furthermore have one or more additives from the group Y, Dy, Hf, Ce, Pr, Nd, Sm, Gd, Ho, Er, Tb, Sb, Nb, W, Yb, Sc and Ta. The production of these electrodes is too expensive. In addition, these electrodes are suitable only for low-pressure discharge lamps with comparatively low operating currents of up to about 50 mA, but not for operating currents of more than 100 mA, as occur in conventional fluorescent lamps.